1. Field of the Invention
The present invention relates to a particle analyzing apparatus, and in particular to a flow cytometer in which a laser light is applied to a hydrodynamically converged portion of a cell-suspended solution flowing at a high speed, wherein the forward scattered light and laterally scattered light or scattered fluorescent light are detected in the sucession to analyze the properties and structure of the cellular particle.
2. Description of the Prior Art
As shown in FIGS. 1 and 2 of the accompanying drawings, in a flow cytometer, a cell-suspended solution flows to a flow section 2 of a minute rectangular cross section (e.g. 70 .mu.m.times.20 .mu.m) in a flow cell 1 together with sheath liquid around said solution, and is hydrodynamically converged. An irradiating light is also converged at the same position, and forward scattered light is detected by a photodetector 8 through a lens 7, while laterally scattered light or fluorescent light is detected by a photodetector 15 through a lens 9.
The form of the irradiating beam in the flow cell is varied according to the size of the particle to be examined or the purpose of analysis. For example, if emphasis is to the examination of morphology of a cell, there is employed a laser beam of a slit form of about 4 .mu.m wide, in order to identify the maximum diameter of the cell and nucleus, ratio of diameter of nucleus to cell, position of nucleus, and whether the cell is a polykaryocyte. On the other hand, the prior art has not generally give particular consideration to the form of the viewing field in the light measuring unit, and the accuracy of analysis cannot be improved due to a possibility of receiving pseudo signals from objects other than the particle to be examined.
More specifically, in FIG. 2, a change in the form of the irradiating beam causes changes in the sizes of the beam in the y- and z-directions in the flow section 2. For example, in case the form of the irradiating beam is so changed as to reduce the size of the beam in the y- and z-directions, the size of the viewing field receiving the light in the z-direction is reduced in the optical system for measuring the laterally scattered light, and same also applies in the x-direction if the particle size is small. Thus, pseudo signals from objects other than the particle to be examined are unavoidable if the form of the viewing field of the measuring optical system is not changed.